Monomers having ethylene-oxide functionalities are commonly known as oxiranes. Oxiranes can be polymerized to form polymers having well-known utility in a variety of practical applications. Nonlimiting examples of the practical applications include dispersing aids, surfactants, and reinforcing fillers.
In order to polymerize oxiranes, any one of the many well-known polymerization methods can be employed. These well-known methods typically utilize alkoxide and hydroxide initiators with alkali-metal counterions other than lithium. However, of the well-known polymerization methods for oxiranes, there are only a few that employ a lithium-containing polymerization initiator. Still further, of those methods that do employ a lithium-containing polymerization initiator, all of them employ the lithium-containing polymerization initiator in combination with polymerization additives. The polymerization additives that are most commonly employed are Lewis acids and Lewis bases. For instance, there are well-known methods for polymerizing ethylene oxide that employ a polystyryllithium initiator in combination with polymerization additives such as dimethyl sulfoxide, KOR+, or P4 base.
In fact, the prior art teaches away from attempting to polymerize oxiranes such as propylene oxide by employing lithium-containing polymerization initiators in reaction mediums devoid of polymerization additives. For example, it has been published, in J. Am. Chem. Soc. 1956, 78, 3432, that attempted polymerization of propylene oxide with a lithium counterion yields no polymer.
Due to the commercial demand for polyoxiranes, there is a need for additional methods directed to their synthesis.